Lawrence Summers has poured gallons of icy water on any remaining optimists. Speaking on a panel at the International Monetary Fund’s annual research conference, the former US Treasury secretary suggested that there could be no easy return to pre-crisis normality in high-income economies. Instead, he sketched out a disturbing future of chronically weak demand and slow economic growth. Mr Summers is not the first to identify the possibility of so-called “secular stagnation”: the fear of emulating Japan’s lost decade has been in the minds of thoughtful analysts since the crisis. But his was a bravura performance.

Why might one believe him? It is possible to point to three relevant features of the western economies.

First, the recovery from the financial crisis of 2007-08 has been decidedly weak. In the third quarter, the US economy was just 5.5 per cent bigger than at its pre-crisis peak, more than five years earlier. US real gross domestic product has continued to decline, relative to the pre-crisis trend. Moreover, such weakness has endured, despite ultra-expansionary monetary policies.